Classical addiction - to drugs, alcohol, gambling, or to other compulsive behaviors - provides the addict with an exoskeleton: boundaries, rituals, timetables, and order in an otherwise chaotically disintegrating universe.
Not so for the narcissist.
Admittedly, like the addict's search for gratification, the narcissist's pursuit of narcissistic supply is frenetic and compulsive and ever-present. Yet, unlike the addict's, it is not structured, rigid, or ritualistic. On the contrary, it is flexible and inventive. Narcissism, in other words, is an adaptive behavior, albeit one that has outlived its usefulness. Addiction is merely self-destructive and has no adaptive value or reason.
Finally, at heart, all addicts are self-destructive, self-defeating, self-loathing, and even suicidal. In other words: addicts are predominantly masochists. Narcissists, in contrast, are sadists and paranoids. They lapse into masochism only when their narcissistic supply runs hopelessly dry. The narcissist's masochism is aimed at restoring his sense of (moral) superiority (as a self-sacrificial victim) and to prod him into a renewed effort to reassert himself and hunt for new sources of narcissistic supply.
Thus, while the addict's brand of masochism is nihilistic and suicidal - the narcissist's masochism is about self-preservation.
(From the book "Malignant Self-love: Narcissism Revisited" by Sam Vaknin - Click on this link to purchase the print book, or 16 e-books, or 2 DVDs with 12 hours of video lectures on narcissists, psychopaths, and abuse in relationships: http://www.narcissistic-abuse.com/thebook.html)